Heretofore, mechanical grippers which engaged the edge of the wafer were used to transfer and seat the wafer at each processing station. After seating the wafer was clamped by overhead fingers extending from a peripheral collar which urged the wafer down against a seating gasket. The overhead fingers interfered with access to the active top surface during processing causing "shadows" in the processed structures. Further, the finger points of pressure created uneven internal stress within the wafer crystal structure.